1. Field of the Invention
The present invention relates to a substrate processing apparatus and a method of manufacturing a semiconductor device.
2. Description of the Related Art
Recently, there has been a tendency to manufacture highly integrated semiconductor devices such as flash memory. Thus, pattern sizes of semiconductor devices become finer and finer. To form such a fine pattern, a predetermined treatment, such as oxidation or nitridation, may be performed on a substrate as a process included in a semiconductor device manufacturing process.
A process of forming a groove between circuits and forming a seed film, a liner film, wires, or the like in the groove is one of methods of forming the pattern. The groove is configured to have a high aspect ratio as pattern sizes become finer and finer.
To form the liner film and the like, it is required to form a high step coverage film in the groove such that the film has a uniform film thickness on an upper side surface, a middle side surface, a lower side surface, and a bottom portion of the groove. By forming the high step coverage film, a semiconductor device may have uniform characteristics between grooves, thereby suppressing a deviation in the characteristics of the semiconductor device.
There have been attempts to process a groove having a high aspect ratio by heating a gas or converting the gas into a plasma state, but a film having high step coverage is difficult to form.
To form a film having high step coverage, an alternate supply method of supplying at least two types of process gases onto a substrate among source gases and reactive gases reacting with the source gases, and reacting the supplied gases together to form a film has been introduced. In the alternate supply method, a film having a desired film thickness is formed by sequentially forming layers of the film by reacting a source gas and a reactive gas with each other on a surface of the substrate such that the formed layers are stacked together to form the film. In this method, a purge process is preferably performed between gas supply processes to remove remnant gases so that the source gas and the reactive gas may not react with each other on locations other than the surface of the substrate.
To uniformize the characteristics of a semiconductor device, a gas needs to be evenly supplied within a plane of a substrate when a thin film is formed. To this end, a single-wafer apparatus capable of evenly supplying a gas onto a surface of the substrate to be processed has been developed. In the single-wafer apparatus, for example, a shower head with a buffer space is installed on the substrate to more evenly supply a gas onto the substrate.
It has been known that in the alternate supply method described above, a remnant gas is purged with a purge gas to suppress gases from reacting with each other on locations other than a surface of a substrate while each of the gases is supplied. However, a film forming time increases when this process is included in the alternate supply method. Thus, a large amount of the purge gas is supplied to discharge the remnant gas in order to reduce a process time.
Although a path or a buffer space may be installed as an example of a shower head for each of various gases to prevent the various gases from being mixed together, the system has a complicated structure. Thus, the system is difficult to maintain and is expensive to manufacture. Accordingly, it is practical to use a shower head in which systems of supplying two types of gases and a system of supplying a purge gas are installed in one buffer space.
When the shower head including a common buffer space for two types of gases is used, it is expected that remnant gases react with each other in the shower head and a deposit is thus accumulated on inner walls of the shower head. To solve this problem, an exhaust unit configured to exhaust the space of a buffer chamber is preferably installed to efficiently remove the remnant gases from the inside of the buffer chamber. In this case, a gas guide configured, for example, to form a desired gas flow is installed in the buffer chamber to prevent two types of gases and a purge gas to be supplied into a process chamber from diffusing toward exhaust holes connected to the exhaust unit. The gas guide is preferably installed, for example, toward a diffusion plate of the shower head in a radial form and between the exhaust holes through which the buffer space is exhausted and gas supply holes through which the two types of gases and the purge gas are supplied. In order to efficiently remove a gas from an inner space of the gas guide, the space between the inside of the gas guide and the exhaust holes for exhausting the buffer space, and particularly, the space between the circumferential edge of the gas guide and the exhaust holes are communicated with one another.